June 18, 2009
Comparative noise study K-7 vs. K20D
Today, I found the time to shoot images from a K-7 and a K20D side by side. In this article, I will highlight the differences in noise between the two cameras.
This is particularly interesting because Pentax used a 2nd generation version of the sensor used in the K20D, a 14.6 MPixel APS-C sensor now famous for its beautiful images when used with an excellent lens.
I am not interested to compare the advances in the camera's built-in JPG engine and its noise reduction (NR) algorithms. I am sure they are significant. I am interested in the best quality I can get from the camera, i.e. from RAW.
- Almost constant lighting, although not perfect (indirect sun light)
- Constant setup:
- My "special" 400% ISO test chart on a wall.
- Constant exposure at EV 9.
- Again, underexposed by ~ -0.7 EV to exhibit more visible noise (to make it "gray").
- Second image underexposed by ~ -1.7 EV (EV 10).
- Tripod, K-7 MLU and K20D 3s timer, both via remote control.
- Zeiss 50mm/1.4 at f/4.0, manually focussed using magnified live view. (The Zeiss 50 is sharper in the center at f/4.0 than f/5.6.)
- Focus series for a resolution test (pending).
- Late sun and wood floor made a nice 3900 Kelvin color temperature.
- Shot in RAW (K20D: PEF, K-7: DNG) and exported by Lightroom using default settings.
- No colors.
- Focus was only almost perfect in the noise test.
- Only one camera of each type tested.
- My camera is a preproduction unit (with final firmware) which may give slightly inferior results to a production camera. Therefore, subtle differences may not be significant.
-- Begin of update --
The interpretation as authorized by Pentax is as follows: Tests carried out with preproduction units and final firmware are allowed to be taken representative of final quality. There won't be a noticeable difference when just inspecting photographs. However, there may be numeric differences when tests are carried out by a quantitative lab test, and if so, in favour of the production cameras. Therefore and because I didn't publish test figures, this blog article must not be considered premature.
-- End of update --
All results are presented as 100% crops prepared for easy inspection here:
Resolution and Noise of K-7 vs. K20D
Please, have a look before joing my conclusion (note that you'll see snippets magnified by 15x!).
The noise from the K-7 and the K20D almost look the same. If there is a slight advantage, then it would go to the K20D. But the difference is so marginal that I say:
There is no significant difference in noise from black & white subjects in raw files from the K-7 and the K20D.
The K-7 produces excellent results up to ISO 1600, and ISO 6400 remains reserved for smaller image sizes. It is however remarkable how much detail is preserved in even ISO 6400!
This is what Pentax is known for: Details rule over noise!